Many researches and developments have been carried out already for moisture absorptive and desorptive paper or, in other words, paper having moisture absorptive and desorptive properties, and the products where substances having moisture absorptive and desorptive properties are contained in paper have been well known. With regard to substance having moisture absorptive and desorptive properties, fibers having moisture absorptive and desorptive properties and fine particles having moisture absorptive and desorptive properties have been much used. As to substances having moisture absorptive and desorptive properties as such, those of organic type and inorganic type are usually available, and there are characteristics that the former has high moisture absorptive and desorptive properties but is swollen while the latter is not swollen although it has little moisture absorptive amount. Therefore, it is not easy to prepare moisture absorptive and desorptive paper in which both high moisture absorptive and desorptive properties and high dimensional stability are available.
With regard to moisture absorptive and desorptive paper where fibers having moisture absorptive and desorptive properties are utilized, there have been known moisture absorptive and desorptive paper comprising a moisture absorptive and desorptive fiber prepared by introduction of cross-linking bond and carboxyl group into an acrylate fiber followed by adding sodium ion thereto, a polyester binder fiber and a conifer pulp, etc. (refer to Japanese Patent Laid-Open No. 06/207398). Since the above-mentioned moisture absorptive and desorptive fiber is able to contain much carboxyl group, it has good moisture absorptive and desorptive properties. Further, since swelling of the above-mentioned moisture absorptive and desorptive fiber is able to be much more suppressed than the ordinary moisture absorptive and desorptive fibers, due to the cross-linking bond, when it is used in small quantity, dimensional stability of the moisture absorptive and desorptive paper is able to be maintained. However, when its using amount is increased for preparing moisture absorptive and desorptive paper having high moisture absorptive and desorptive properties, the resulting suppressive action for swelling is not sufficient and lowering in its dimensional stability is unavoidable. Accordingly, in the moisture absorptive and desorptive paper disclosed in said document, improvement in the dimensional stability is attempted by the use of large amount of binder fiber or by the application of a hot press after making into paper. However, when the binder fiber is used in large amount, the moisture absorptive and desorptive fiber is covered with a fused binder fiber and bound, whereby even when the moisture absorptive and desorptive properties inherent to the moisture absorptive and desorptive fiber are good, the expected properties are unable to be well achieved and it is difficult to enhance the moisture absorptive and desorptive properties as the moisture absorptive and desorptive paper.
With regard to examples where fine particles having moisture absorptive and desorptive properties are used, there have been known moisture absorptive and desorptive paper comprising inorganic particles such as silica gel or zeolite, wood pulp and thermally adhesive fiber, etc. (refer to Japanese Patent Laid-Open No. 10/212,692). Said moisture absorptive and desorptive paper is not swollen even when inorganic particles playing a role of moisture absorptive and desorptive properties such as silica gel or zeolite absorbs moisture, whereby it is satisfactory in terms of dimensional stability. However, as mentioned already, since inorganic particles have small moisture-absorbing amount, it is difficult to prepare moisture absorptive and desorptive paper having high moisture absorptive and desorptive properties and, in addition, there is a disadvantage that moisture absorptive rate is slow, high temperature is needed for moisture desorption, or the particles are crushed upon repeated moisture absorption and desorption to lowering the properties, whereby its utilizing fields are limited.